Contact Lens for Keratoconus: Soft Custom Lens vs RGP vs Scleral Lenses

Contact Lens for Keratoconus:  Soft Custom Lens vs RGP vs Scleral Lenses

So we know that the corneas of keratoconus become thinner and irregular in shape. The cornea becomes steeper or more curved. How does this relate to vision? When light hits the irregularly thin cornea, light scatters and does not focus correctly on the retina. Irregular astigmatism and nearsightedness make vision blurry. People with keratoconus often cannot see distant things clearly and need to move their mobile phones or computers just a couple of inches away from their noses.

For mild stages, eyeglasses or conventional soft contact lenses may suffice. However, adding the prescription will not improve your vision for moderate to severe cases. This is where specialty contact lenses come in.

In today’s article, we will be discussing the pros and cons of the following specialty lenses: customized soft lenses for keratoconus, small GP lenses (RGP), and scleral lenses.

Customized Soft Lenses for Keratoconus


Unlike the simple, off-the-shelf contact lenses fitted for standard eye grade, this type of customized soft contact lens is made with a thicker material that can hide some of your irregular astigmatism. However, because it is still a soft lens, the amount of astigmatism that it can mask is still limited. In addition, for stability, this is slightly larger than regular soft contact lenses.

Pros
Easy to handle
Convenient
Comfortable on eye

Cons
Not for advanced stages of keratoconus.
Vision may not be as clear as gas permeable or scleral lenses.
Need to be replaced frequently (every 3 to 4 months)
Cost more

Small GP Contact Lens (RGP)

GPs are hard lenses made from oxygen-permeable materials. The size can be 7.5mm to 11.2mm in diameter. Because it is made with a rigid material, it provides a smooth surface to allow the light to enter the eye and forms a more focused image. This helps immensely in allowing you to see clearer. Small GPs may be fitted with a soft lens underneath to improve the fit or comfort. This combination is called piggyback system.

Pros
Provides good vision clarity
It can last longer depending on the stability of the condition
Convenient
Cheaper

Cons
Not comfortable for some, requires an adaptation period
May displace on eye
Not suitable for severe cases

Scleral Contact Lens

Scleral Contact Lenses

Gold Heart Optical Centre Dry Eye Management

On the other hand, scleral lenses are also made from a gas permeable material but bigger than conventional GPs. A scleral lens may be as small as 14.5 to as large as 24mm. Like GPs, this lens acts as an artificial surface to allow the light to enter smoothly and focus better on the retina. So vision becomes more precise. However, it is different from a small GP lens in its fitting. Scleral lens vaults the entire cornea, which means there is a sizeable distance from the back part of the lens to the corneal surface. This liquid-filled space allows the scleral lens to be fitted in even the most severe cases. Also, due to its size, the eyelids do not have constant interaction with the lens edge, so it is more comfortable than a GP.

Pros
Comfortable
Provides good clarity and more stable vision
Can be fitted with reading grade for those 40 years old and above
Suitable for mild to severe cases
Can last longer
Helps in dry eye patients

Cons
Learning curve in handling
Cost more

 

About the Doctor:

Dr. Millette Romualdez is a Fellow of the American Academy of Optometry, Scleral Lens Society, Philippine College of Optometry and International Association of Contact Lens Educators. She has also received a Certification of Advanced Contact Lenses from the Australian College of Optometry.

To book an appointment for a doctor that fits keratoconus contact lenses such as scleral contact lenses, GP lenses and Kerasoft IC , contact us via 09215452389 or docmillette@goldheartoptical.com.

 

 

What is Keratoconus?

KERATOCONUS 

WHAT IS KERATOCONUS?

 According to the American Optometric Association, KERATOCONUS is a condition that occurs when the normally round cornea (outer, transparent part of the eye) becomes thin and cone-shaped.  This irregularity prevents the light entering the eye from being focused correctly on the retina which then causes distortion and blurring of vision.

Growing up, parents would notice that there was a need to change the prescription of their child more frequently.  It seemed that the prescription was always taken incorrectly, and your child’s astigmatism and nearsightedness got higher with each vision examination. Then eventually, the prescription was not enough to provide the patient with the usual coveted 20/20 perfect vision with their glasses or conventional contact lenses.  And it is because a person with keratoconus would usually not achieve the 20/20 vision, many would mistake the condition as a simple amblyopia or lazy eyes. A keratoconic cornea becomes irregular thus the astigmatism created is also irregular, causing conventional glasses or contact lenses to be unsuitable for correction.

How many people have keratoconus?

Originally, keratoconus was deemed rare, having an incidence of 1:2000 during a published study in 1986. However, recently, a study involving the population in the Netherlands resulted in a prevalence of  1:375 of keratoconus in the general population.  Over the years, we have seen a greater amount of keratoconus referrals and realized that indeed this condition is not at all rare, with a pool of patients being detected during the screening for refractive surgery consults.

How keratoconus can be managed?

Corneal Collagen Cross Linking

Usually, the protocol in managing keratoconus patients would include a discussion about corneal collagen cross-linking that aims in controlling the worsening of the disease. If there is an indication that the keratoconus of the patient is progressing, collagen cross-linking may be performed. In collagen cross-linking, riboflavin (vitamin B2) is administered in conjunction with ultraviolet A which leads to biomechanical stiffening of the cornea.   It was shown that this procedure flattens the cornea by about 2 Diopters and may improve vision to about 2 lines or 10 letters.  Some patients would delay this procedure, but note that there is a minimum cut-off corneal thickness for the surgeon to still allow to do the procedure for safety purposes.

Intrastromal Corneal Ring Segments

These are small, crescent-shaped plastic rings that are placed in the deep, peripheral corneal stroma in order to flatten the cornea. They are made of polymethylmethacrylate (PMMA).   This too may flatten the cornea to about 2 Diopters, and may improve uncorrected vision to about 2 – 4 lines as noted in different studies. This is not a must in the keratoconus management, however, it may be indicated if contact lenses cannot be fitted due to the very steep cornea.

Corneal Transplants

In the worst cases, corneal transplantations are considered. Only about 10-28% of keratoconus patients would need corneal transplantation to improve their vision.   Corneal transplant is only indicated if vision cannot be improved anymore with contact lenses and if lenses are intolerable already.  The average long-term graft survival is nearly 20 years.  This means that a young patient can have more than one corneal transplant in a lifetime. Vision with correction will definitely be improved however note that uncorrected, patient may still have astigmatism. If your keratoconus was severe before the transplantation, it is possible for you to see a dramatic change in your uncorrected vision. Some patients may be happy with their uncorrected vision post the transplant, but most would still need contact lenses to achieve good vision.

Special Designed Contact Lenses

RGP for Keratoconus

In general, to attain good vision, specially designed contact lenses would still be needed after the collagen cross-linking, intrastromal ring implantation and corneal transplant.  This is why, before considering corneal transplants, all contact lens options should be exhausted to see if vision can still be satisfactory with them.    Most often than not, one can achieve good vision with contact lenses.  Attaining a 20/20 vision is not impossible but it is also not the default. It all depends on the severity of the condition and if the cornea does not have scars. 

What are the different types of contact lenses for keratoconus?

Scleral Contact Lenses

Special contact lenses include small GP (gas permeable) lenses, large GP lenses (scleral lens), soft customized contact lenses and hybrid contact lenses.  Small gas permeable lenses, hybrid contact lenses and Keraosft IC soft customized contact lenses are indicated for mild to moderate cases, while scleral contact lenses are often used for patients who cannot tolerate small gas permeable lenses and for all stages of keratoconus.

Here is the link  https://goldheartoptical.com/scleral-lens-and-kerasoft-ic-fitting/ to know more about the different types of contact lenses for keratoconus and to get a copy of the FAQs on Keratoconus.

 

References:  

  1. Javadi M. A., Motlagh B. F., Jafarinasab M. R., et al. Outcomes of penetrating keratoplasty in keratoconus. Cornea. 2005;24(8):941–946. doi: 10.1097/01.ico.0000159730.45177.cd.
  2.    Sykakis E et al.Corneal Collagen Cross-linking for treating keratoconus.  Cochrane Database Syst Rev. 2015 Mar 24;93): CD010621.
  1. Wollensak G, Spoerl E, Seiler T. Stress-strain measurements of human and porcine corneas after riboflavin-ultraviolet-A induced cross-linking.Journal of Cataract and Refractive Surgery.  2003;29(9):1780-1785.
  1. Zadnik K, Money S, Lindsley K.Intrastromal corneal ring segments for treating keratoconus. Cochrane Database Sys Rev. 2019 May 14.
  1. Kelly T, Williams KA, Coster DJ, Australian Corneal Graft Registry. Corneal Transplantation for Keratoconus: A Registry Study. Arch Ophthalmol.2011;129(6):691–697. doi:10.1001/archophthalmol.2011.7
  1.  Kennedy RH, Bourne WM, Dyer JA, 1986. A 48-year clinical and epidemiologic study of keratoconus. Am. J. Ophthalmol101, 267–273.
  1. Godefrooij DA et al.Age-specific Incidence and Prevalence of Keratoconus:  A Nationwide Registration Study. Am J Ophthalmol. 2017 Mar; 175:169-172.
  1. Grentzelos MA, Kounis GA, Diakonis VF, Siganos CS, Tsilimbaris MK, Pallikaris IG, Kymionis GD, 2017. Combined transepithelial phototherapeutic keratectomy and conventional photorefractive keratectomy followed simultaneously by corneal crosslinking for keratoconus: cretan protocol plus. J. Cataract Refract. Surg43, 1257–1262

 

About the Doctor:

Dr. Millette Romualdez is a Fellow of the American Academy of Optometry, Scleral Lens Society, Philippine College of Optometry and International Association of Contact Lens Educators. She has also received a Certification of Advanced Contact Lenses from the Australian College of Optometry.

To book an appointment for a doctor that fits keratoconus contact lenses such as scleral contact lenses, GP lenses and Kerasoft IC , contact us via 09215452389 or docmillette@goldheartoptical.com.